Conventionally, as a biological observation apparatus, an endoscope apparatus which irradiates illumination light and obtains an endoscope image in a body cavity has been widely used. In an endoscope apparatus of this kind, an electronic endoscope having image pick up means which guides illumination light from a light source into a body cavity by using a light guide or the like and picks up an image of a subject by its feedback light, and by performing signal processing of an image pickup signal from the image pickup means by a video processor, the endoscope image is displayed on an observation monitor so that an observation region of a patient or the like is observed.
When ordinary biological tissue observation is performed in an endoscope apparatus, in one method, white light in a visible light region is emitted with a light source device, frame sequential light is irradiated to a subject via a revolving filter of R, G, B and the like, for example, feedback light by the frame sequential light is synchronized by a video processor and is subjected to image processing, whereby a color image is obtained. When ordinary biological tissue observation is performed in an endoscope apparatus, in another method, color chips are distributed to a front surface of an image pickup surface of image pickup means of an endoscope, white light in a visible light region is emitted with a light source device, an image is picked up by separating feedback light by the white light in accordance with color components with the color chips, and image processing is performed with a video processor, whereby a color image is obtained.
Since a biological tissue differs in light absorption characteristic and scattering characteristic depending on the wavelength of irradiated light, for example, Japanese Patent Laid-Open No. 2002-95635 discloses a narrow band light endoscope apparatus which irradiates a biological tissue with illumination light in a visible light region and narrow band RGB sequential light with discrete spectral characteristics, and obtains tissue information of a desired deep portion of the biological tissue.
Japanese Patent Laid-Open No. 2003-93336 discloses an electronic endoscope apparatus which applies signal processing to an image signal by illumination light in a visible light region to create a discrete spectral image, and obtains image information of a biological tissue.
However, for example, in the apparatus disclosed in the above described Japanese Patent Laid-Open No. 2003-93336, an spectral image is obtained by signal processing, and a filter for generating narrow band RGB light is not required, but since the obtained spectral image is simply outputted to a monitor, there arises a fear that the image displayed on the monitor does not become an image of a color tone suitable for observation of tissue information of a desired deep portion of a biological tissue.
In the apparatus disclosed in Japanese Patent Laid-Open No. 2002-95635, an optically narrow band bandpass filter is used. However, in the apparatus disclosed in Japanese Patent Laid-Open No. 2003-93336, a narrow band spectral image signal (also called a spectral signal) is created by signal processing without using an optically narrow band filter.
However, in the apparatus disclosed in Japanese Patent Laid-Open No. 2003-93336, processing of creating a spectral signal which is obtained in the case of using a narrow-band bandpass filter is performed by electrical computation processing by matrix computation from a color image signal (corresponding to a quasi-bandpass filter) picked up in a wide wavelength band without using an optically narrow band bandpass filter, and therefore, the spectral characteristic of illumination light which is generated with a light source and irradiated to a biological tissue has a large influence, but the prior art example only discloses the use of only one lamp.
Therefore, there is a disadvantage of securing precision or reliability of a spectral signal electrically generated.
The present invention is made in view of the above described circumstances, and has an object to provide a signal processing device for a biological observation apparatus which can adjust tissue information of a desired deep portion of a biological tissue based on a spectral image obtained by signal processing to image information in a color tone suitable for observation.
Further, the present invention has an object to provide a biological observation apparatus including a function of electrically creating a spectral signal from a biological signal, and suitable for obtaining a spectral signal with higher precision or reliability.